In recent years, environmental pollution caused by discarding plastics, global warming due to gasses generated in incineration of plastics, and the like have been problematic. Under such circumstances, for example, polylactic acid obtained by polymerization of lactic acid produced by fermentation of starch or the like, and the like have attracted attention as biodegradable plastics and carbon neutral materials (Patent Documents 1 and 2). Herein, the term “carbon neutral material” refers to a material which yields a small amount of discharge of carbon dioxide gas during the entire life cycle (from collecting the raw material until disposal).
The polylactic acid obtained from carbohydrates (starch and the like) produced by plants are accompanied by significantly smaller amount of a carbon dioxide gas generated during time periods from the manufacturing step to disposal step, as compared with general resins derived from petroleum (i.e., being carbon neutral).
Furthermore, similarly to polylactic acid, poly(3-hydroxybutyrate) polymers have also attracted attention (Patent Documents 3 and 4). The poly(3-hydroxybutyrate) polymers can be produced, for example, using a microorganism, from a methane gas obtained by fermentation of organic wastes such as garbage, food wastes and livestock excreta under anaerobic conditions, or from plant raw materials. In addition, the poly(3-hydroxybutyrate) polymers are biodegradable after the disposal, or are turned back to the methane gas by microorganisms, therefore, they are recyclable and environmentally friendly plastics.
Moreover, polybutylene succinate polymers have also attracted attention as materials accompanied by a smaller amount of carbon dioxide gas discharged, as compared with general resins derived from petroleum (Patent Document 5). The polybutylene succinate polymer can be manufacture by, for example, using succinic acid and a diol component as raw materials, and the succinic acid can be manufactured by fermentation of a saccharide such as sugarcane or maize.
As described in the foregoing, a variety of plastics constituted using a material derived from a non-petroleum source taking into consideration the environment have been developed so far. However, these plastics are inferior in flexibility, rubber elasticity, compression set property and the like, and many of these are also accompanied by difficulties in molding processing, whereby their applicable scope has been restricted.
Patent Document 1: Japanese Unexamined Patent Application, First Publication No. 2002-275303
Patent Document 2: Japanese Unexamined Patent Application, First Publication No. 2002-040598
Patent Document 3: Japanese Unexamined Patent Application, First Publication No. 2006-045366
Patent Document 4: Japanese Unexamined Patent Application, First Publication No. 2005-304484
Patent Document 5: Japanese Unexamined Patent Application, First Publication No. 2005-211041